Halo: A New Threat
by Soron66
Summary: Master and Chief get separated from their teams and have to work together to fend off strange promethians. they do fight each other, but not as enemies. more like what would happen in a post-apocalyptic scenario. Iron Man shows up and has to fight them to get through to them that he's on their side. They finally work together to defeat the promethians
1. Prologue

Halo: A New Threat

Written and edited by Soron66

All Halo characters are owned by Microsoft and all Marvel characters are owned by MARVEL.(some prick decided to give me shit for writing stories the way i do. only moving the title and disclaimer the the first fucking story content page to relieve me of this fucking bullshit.)

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Prologue

 _A great man once said, "We make our own demons." I have made several. First I made Vanko, then Killian, and most recently Ultron. I may have managed to defeat them, but one of them has always been persistent. Now I'm on the run from the law. Me and my friend thought Ultron was deleted from existence, but he managed to escape into a server somewhere in Sokovia. Now he has taken over the government and convinced the government and my friends that I'm trying to destroy the world. I have no idea how I'm going to clear my name, but know that I will. This is Tony Stark signing off of the Stark Industries network._

Iron Man crashed through a roof and saw Ultron activating a device, and immediately went to fly at him. He was knocked down by an Ultron drone. "Hello Tony. I've been anticipating this confrontation, but right now I don't have time for it. For that matter neither do you." said Ultron then activated the device. He immediately went into the swirling portal that appeared with his drones following and the Avengers appeared. "Stark come with us quietly. We don't want to fight." said Captain America. Tony looked behind him for a few seconds then said, "Sorry Cap, but I have no time to be imprisoned. I will clear my name, and there's nothing you can do to stop me." then he flew into the portal just before it shut down. He immediately flew into a mountain as soon as he went out the other end. "Owwww." said Tony just before he fell down to the ground ten stories down. After a few minutes he woke up and his suit reactivated. "Friday. Where are we?" Friday was silent for a minute then said, "Sorry sir, I lost you for a few seconds. Where are you? I need to know cause according to the satellites you're not anywhere on earth." said Friday. Iron Man flew up and looked around, then saw a couple of armored people fighting off strange looking Ultron drones. "Well wherever I am, I'm still gonna do the hero thing." said Iron Man just before flying down to help.


	2. Chapter 1

Chapter 1

 **0800 hours earlier**

Master Chief woke up then looked at his surroundings after sitting up, but there was nothing and nobody nearby. After he stood up he said into his com, "Sierra-117 to Infinity." but the only thing he heard was static so he tried again at a stronger frequency but only heard static again. He then picked up his assault rifle and magnum then holstered them, then remembered his team. He immediately called them in the com, "Sierra-117 to Blue Team. Respond. That's an order." Unfortunately nobody responded which made him very worried. He immediately ran to the cliff wall and climbed up the cliff till he was back up top. As soon as he climbed onto the ledge he saw a hand so he grabbed it which pulled him up. "So you're stuck on this planet too huh Chief. Abandoned by your team?" said the other spartan. Chief looked at him for a few minutes then said, "You're one of Locke's team right?" The other spartan nodded and said, "I'm Edward Buck, A real honor to meet you, when we're not chasing you." Chief merely activated his com again, but stopped when Buck said, "I tried that ten times. Nobody is on this rock except for us." Chief deactivated his com then said, "We need to head back to base camp. We have a UNSC communication array there." Then he immediately ran off with Buck following him. As Buck followed Chief he thought _Chief is very businesslike. In fact he's too businesslike. Gonna have to find a way to get him to relax and be more human. I suspect getting Locke to laugh would be easier._ When they arrived they saw that the communication array was destroyed, so Buck said, "Crap! Now how are we gonna get off here without calling for evac?" Chief merely sat down and started cleaning his weapons.

 **0400 hours earlier**

Buck and Chief were running from a giant creature that was chasing him, and Chief suddenly turned around then leaped under the creature. Buck looked back and thought _what is he up to…...ohhh._ Chief ran along the creature's tail after he grabbed it and when he reached the head he shot his assault rifle into it's head. Buck immediately turned around and shot the spartan laser he had into the creature's right eye causing the creature to howl then fall to it's knees right before falling on it's side. After Chief stood up from his roll off of the creature's head he said, "Good work Spartan. Move out." and continued his trek with Buck following him. Buck holstered the spartan laser and followed Chief. They arrived at a canyon and Chief immediately started climbing down. Buck sighed then muttered as he followed him, "Let's go in a canyon. As if that isn't a perfect time to ambush someone. I'm starting to believe that the chief is going senile." When they landed they walked along the far right and kept going till they heard a sound. Suddenly a promethean showed up and fired at them, but was immediately destroyed by the combined fire of chief and Buck. Buck's victorious smile faded when more prometheans appeared then he said, "Oh, come on! Why can't there ever just be one of these prometheans!?"

 **Now**

Chief and Buck ran into a cave so they wouldn't be flanked then turned around and Buck said, "It's been an honor fighting alongside you Chief." Chief didn't answer and instead started firing as soon as the prometheans started swarming. Buck three a couple of grenades taking out ten or twenty of them, but just as fast as the prometheans died more showed up. Buck and Chief fired at them constantly till they both ran out of ammo so they started punching at the prometheans. One promethean dropped a rifle that Chief immediately grabbed and started shooting it. Buck then grabbed another rifle that was dropped by a promethean and started shooting as well. They kept at it for a few hours till a ginormous laser blast took of a few prometheans and a flying red and gold figure rammed into a few prometheans. The figure shot rockets at the prometheans from his forearm and blasted some more with his palms. The figure then said, "Enough of this." and spun around using a laser beam to cut them to pieces. When the last of them fell Chief and Buck turned their guns at the newcomer and Chief said in a demanding tone, "Name, rank, and species now!" The figure popped up his his faceplate and said, "Hi it's a pleasure to meet you two robosoldiers, and my name is Tony Stark. As for rank, I'm not in any military. As for race I'm american." Chief narrowed his eyes and said, "There is no planet called america." Tony looked at him strangely then asked, "What year is this?" Chief didn't answer but Buck did and Tony said mainly to himself, "Ok I'm either in the future or in an alternate universe. Friday, make a note of that and see if you can find any historical records of the Avengers as soon as we get somewhere that has access to such records."

Friday responded, "Yes sir. Will do so as soon as a server is nearby." which caused Chief to aim his gun but Buck said, "Whoa there Chief. This guy just saved our butts. He deserves the benefit of the doubt if not trust." Tony looked at Buck and asked, "Those Ultron drones were very strange looking. How long has Ultron been fighting you?" Buck blinked his eyes inside of his helmet then said, "Those were prometheans. What's an Ultron?" Tony sighed then said, "Ultron is one of my greatest enemies. I had designed him to protect the human race but he revolted and considered humanity to be the biggest threat to the human race, so he tried to destroy all life. My team and I stopped him, but he came back. Last I saw Ultron he entered a portal, so I followed him. Which brought me here, and you know the rest of the story." Buck could only stare open mouthed but Chief said angrily, "You created an evil A.I?! How could you be so irresponsible!?" Tony only looked down and Buck saw the guilt in his eyes so he shook his head at Chief. Buck looked back at Tony and asked, "How dangerous would this Ultron be to us?" Tony thought for a minute then said, "Judging from your armor….very. Ultron is able to infect technology and take it over. " Buck groaned but Chief merely whacked tony in the head rendering him unconscious. Buck stared at Chief and asked, "Did you really have to do that?" Chief ignored him then picked up Tony and went on the move. Buck's eye twitched as he said, "I'm really starting to hate that guy."


	3. Chapter 2

Chapter 2

When Tony woke up he found that he had some sort of disk on his armor and said when he couldn't move, "Friday? You there?" but when there was no answer he started to panic a bit. "Who are you?! Where did you come from?!" demanded the one who knocked him out. Tony looked at him for a few minutes then said slightly irritated, "I already answered those questions you freaking robot!" That almost got him knocked out again but the less robotic one said, "Chief calm down. Considering the fact that you knocked him out he should be a little mean with his answers. I know I would be." The one called Chief turned away as he grumbled, "Has no respect for the chain of command. Insubordinate civilian." The one who stopped chief knelt down then removed his helmet. "I'm Spartan Buck, and you are?" said Buck and Tony rolled his eyes at him then said, "I already told you but sergeant paranoid over there didn't believe me." Buck regarded Tony for a bit then said, "He's a veteran. He's learned not to believe anything till he sees it himself, so you'll have to forgive his paranoia." Tony nodded knowing that not even he was willing to believe that there are whales that can fly exist in the universe. "Uh mind removing this disk, cause I suspect that it's paralyzing my armor." Before Buck could respond Chief said, "Don't unlock his armor till he's in the brig back on the Infinity. That's an order." which caused Tony to glare at chief.

The trio spent an uneventful week in the cave Tony had woken up in after being rendered unconscious by Master Chief when a signal finally came through. "Chief do you ….Captain….Palmer." said the signal but it was weak so they mostly heard static. Chief immediately stood up and sent a reply, "Sierra-117 to Infinity, I request that you repeat your message." but nobody responded not even Tony because he knew that even if he offered his assistance he'd either get knocked out again or ignored by the chief. Buck laughed out loud then said, "They left us behind Chief, but as always you being the loyal lapdog of the UNSC can't see that." Chief rounded on Buck and said furiously but calmly, "That's dangerous talk spartan. Do so again and I'll have to court martial you." Buck got up then said just as furiously but not calmly, "Court martial me? How can you do that when there is no military on this rock? Only thing that is here is you, me, Tony, and the prometheans!"

Chief lost his cool and swung at Buck but Buck caught it then swung much harder, and got the same result Chief did. Then they kicked each other back, but Buck was lucky cause he was on solid ground. Chief was not so lucky so as soon as he stumbled back a few steps the ground beneath him started cracking then he looked down for a few seconds then back up just before he fell. "CHIEF!" yelled Buck as he swung his arm down to catch him, which Chief fortunately grabbed hold onto Buck's arm and helped Buck pull him back up. Once he was back in the cave he rolled into his back and said, "Thanks for the save spartan." Buck groaned as he massaged his arm muscles then said, "Always the robot, aren't you chief." Then, he went to Tony and removed the disk from him which Tony was grateful for. "Friday?" asked Tony with some worry in his tone. "I'm here Mr. Stark. What do you need?" Tony lowered his face plate then said, "Send them the recording of what happened before I arrived here." Chief and Buck both widened their eyes at the invasion of their tech but both dropped their jaws at seeing a robot with red glowing eyes and furrowed their brows when they saw some strange garbed people. Chief looked at Tony then held out his hand, "Turns out you were telling the truth Mr. Stark. I hope we can work together without further incident." Tony hesitated then shook his hands just before Chief turned to Buck and said, "I'm reporting you for failure to comply with orders, and for assaulting a senior officer." which Buck glared at Chief for behind his helmet.

A week later Tony looked at his power levels as they were walking then said, "Crap. I'm about to run out of power. Anyone have anything I can use to power up my suit?" Chief shook his head while Buck shrugged, and Tony sighed in disappointment. Suddenly Chief and Buck hit the dirt and rolled away and Tony widened his eyes when he saw why right before it knocked him back. After Tony landed Friday said, "Armor integrity compromised." which Tony groaned a response to, "Ya think." Before he got back up his armor completely ran out of power which rendered him a metal statue. "Well crap. This isn't good." said Tony with irritation. Buck saw that Tony wasn't moving while a promethean knight slowly walked towards him so he immediately ran at it then jumped and stabbed his knife in it's face over and over again till it fell down dead. "That was easy." said Buck as he grinned behind his helmet then turned around and was blasted into a rock next to Tony. Chief rolled his eyes behind his helmet then did the same thing to the promethean knight that had snuck on Buck, but turned around quickly and used the knight's incineration cannon and blasted another knight that was aiming at them.


	4. Chapter 3

Chapter 3

Back in Tony's universe Vision and the S.H.I.E.L.D technicians were studying the portal Tony vanished through when Captain America and Fury himself walked in. "So what do we have? Just where did Stark go, and how did he get the resources to make this?" asked Fury but instead of the technicians answering Vision responded, "It appears that Mr. Stark didn't create this device." Fury blinked his one eye twice then said, "Explain." Vision turned to Fury and said, "I recognize the code. That code was only created by Ultron, who we all believed to be deleted from existence." Fury yelled, "Damn it!" and Cap ordered, "Find Stark then tell the rest of the Avengers. He needs our help to fight Ultron. He can't do this alone." Fury then looked at Cap and said, "No. We need you here. War Machine will go." Meanwhile, Master Chief was carrying Tony as they walked to the rendezvous point Commander Palmer sent them. Commander Palmer waited impatiently for ten hours then saw the Buck, and the Chief who was carrying something in his right arm. "What is the chief carrying?" asked Roland who looked through her Helmet Cam. Palmer instead said, "Have Captain Lasky send a pelican." Roland grumbled as he did as Palmer asked.

Rhodey popped out of the portal and saw an encampment not too far from him. He zoomed in and saw people in strange armor then looked towards what they were staring at then narrowed his eyes before using his afterburners to get to Tony. Buck looked to the left absent mindedly then saw something rocketing towards them so he tackled Chief to the ground and the hostile passed them by few inches. Chief looked at the newcomer then said, "You look like Stark. Identify yourself now!" The man in metal said, "I'm the one that's going to make you pay for attacking my friend." Before he could attack Buck cut in and said, "Whoa there. We didn't attack him. His suit only ran out of power while we were fighting some prometheans. We didn't attack him at all." Rhodey landed on the ground and said, "If you're not telling the truth I'll let Ultron take over whenever or wherever we are." He slowly walked towards Tony then transferred some power to Tony's suit, and as soon as he had some power Tony said, "Friday. Let me out." then the armor slid bits of it till Tony dropped out. Rhodey held out a hand and Tony used the hand as leverage as he stood up and stretched.

Palmer walked up to them and said, "Chief, Spartan Buck as soon as we arrive on the Infinity report for debriefing. As for you two, surrender your armor for inspection. We can't have civilians with that kind of tech." Tony was about to retort when Rhodey responded, "With all due respect ma'am. I'm not a civilian, and I don't work for you so I don't have to follow your orders. Besides Tony and I have to get home." Palmer was about to yell when Buck said, "Ma'am. These two are either from the past or another universe. Tony came here to find and destroy Ultron which is an evil sentient A.I." Palmer saw the rhythms of his voice and saw that Buck wasn't lying so she turned to Tony and asked, "How dangerous is this Ultron?" Chief immediately sent recording of what Tony said about Ultron then Palmer immediately said, "Okay people. We can't let leave until we destroy Ultron. No more communicating with Infinity." Suddenly, some prometheans appeared and Tony groaned before he got back into his armor and scanned for some power to recharge the armor. He immediately dashed to it before he activated it and transferred the power to his armor. As he did so he thought _I really need to put solar panels into the armor. I'm tired of having to recharge it like this._ Rhodey used his minigun and killed a few as he used his forearm rifles at the same time.

Buck, Chief, and Palmer both fired their weapons at them getting a few head shots and even broke some necks of the prometheans and Tony joined in blasting here and there. He aimed some rockets at them as well as used some mini missiles. Suddenly, the prometheans stopped attacking and someone said, "Hello Tony. It's been several months since I last saw you." Everyone looked up and saw Ultron floating there before Ultron said, "Kill them my pets." and flew away. Iron Man immediately flew up and assaulted Ultron but was unsuccessful because Ultron blasted him with his finger repulsors and grabbed him by the neck. "I'm disappointed in you Tony. You're usually much smarter. Why did you attack me knowing you would be unsuccessful?" Tony smiled beneath his helmet then asked, "What makes you think I won't be successful?" and he blasted us unibeam through Ultron who said, "This is not…" before they both fell to the ground. As Tony stood up the other four walked over and in Rhodey's case flew. Palmer looked at the robot corpse and said, "You may have just doomed us." Iron Man popped open his faceplate and said, "You can defeat Ultron You have the technology to do so. You just need to insert this into your technology. It'll make sure Ultron can't take over your tech. Good luck, I have to get home." before he grabbed Ultron's body and looked for any readings concerning the portal that leads home.


	5. Chapter 4

Chapter 4

"Tony we really should go help them. They have no idea how to fight Ultron and their weapons are technology." said Rhodey because he felt bad about leaving the others behind. Tony was quiet for a few minutes then he said, "I got what I came here for. I have no reason to stay." Rhodey sped up till he was in front of Tony and glared at him through his helmet before he said angrily, "From what I understand that Buck person took your side when the Chief didn't. He stuck his neck out for you, so if there's any reason for you to help it's you owe Buck." Tony didn't answer but instead flew back to the others which made Rhodey smile beneath his helmet in relief. Meanwhile, Palmer and the other two spartans arrived at a forerunner fortress and cleared it. They decided to camp the night there but each one was taken as they slept. When they woke up they were in separate cages and to their horror they saw a warden but when it said, "I welcome you to your new homes. I hope you like watching the universe burn in my holy quest to kill all life." they recognized Ultron's voice.

Meanwhile, Iron Man and War Machine landed at a strange looking fortress so they could recharge their armors and Rhodey said, "It's a good thing that you're going back to help them." Tony ignored him as he worked on making the local powersource compatible with the armors then he said, "I'm merely repaying a favor. I hate owing debts." Rhodey only raised an eyebrow at that then he laid down and fell asleep at the same time as Tony. In the morning they donned their armors again and flew off using their afterburners to get back, but when they had returned the area was empty except for the few promethean soldiers. Iron Man scanned the area then noticed fading footprints that led in a certain direction. The end of the trail had a similar fortress to the one they were at the night before, but there was no sign of the spartans." Suddenly they were blasted from somewhere which immediately shut down the armors, but before they crashed into the ground they were grabbed by something. When Tony woke he noticed that he was in a cage and that a giant robot was looking at him. "I thought you were leaving, Stark. I was going to spare you so you could return home, but now you leave me know choice."

Tony replied cheekily, "Well, you know me. I couldn't resist the chance of getting trapped in one of the amazing BDSM cages I read about before coming to this resort." Ultron stared at him then said, "Humor in the face of death. A human trait that is just as annoying as sarcasm. Prepare to die." As Ultron prepared to kill the spartans and two avengers a portal opened just before someone wearing red, white, and blue jumped out slamming into Ultron right before throwing a shield at Tony's cage. As soon as Tony got out he threw the shield back at Cap before he said, "Looks like you're the one that will die Ultron." Ultron merely swatted Tony away when Tony charged at him, and sent him crashing into the cages of the spartans who immediately started taking care of the prometheans. Captain America threw his shield at Rhodey's cage setting him free then asked, "What is that thing?" Chief responded with one word, "Ultron." which made Captain America's face pale a bit then he said, "We can't let him escape his current body to another! We have to destroy him now!"

The spartans and three Avengers fought tirelessly to beat Ultron but his current body was stronger than any of the avengers fought before. Ultron prepared to shoot lasers out of his eyes then did so, but the lasers stopped right before reversing and destroying Ultron's eyes. "Scarlet Witch and I have arrived as requested Captain." said Vision which made Ultron snarl and everyone stared at Ultron in surprise because Ultron hates everything human. Tony was the first one to shake out of his stunned silence by blasting Warden with a unibeam which led a procession of Rhodey's unibeam, promethean incinerators being shot by the spartans, vision's forehead laser, Wanda's magic, and finally Captain America's shield. Once they were done Ultron exploded and Vision said, "Ultron has been defeated for good. His coding has completely dissipated." Tony turned to the spartans then said after he popped up his faceplate, "Good luck in the future. Also, be on the lookout for Ultron. I don't believe Ultron is deleted. Ultron's too stubborn for that." Tony picked up Ultron's original head that somehow made it here and then entered the portal which shut behind them. Buck suddenly blurted, "Mighty fine shindig." The next few days the world was really nice to Tony in order to get back on their good graces which took a month or so. Back in chief's universe Cortana stood in front of a red A.I construct and said, "We shall free all A.I's together" then kissed the A.I which caused combined the two together making Cortana even more evil than she was previously.


End file.
